[feat gw-api]bugfix and prevent backward generation route status update

[shuqz]

Description

1. fix for getting impacted gateway for route update, current setup only takes new parentRef from route, which left previous parentRefs do not have gateway reconcile triggered-> modified GetImpactedGatewaysFromParentRefs for this
2. added additional check in route reconciler so status won't be updated if the new generation is less than current route generation -> introduced GetRouteGeneration for this

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested
  • tested No.1 by printing out impacted gateways for following case: originally have GW1 and GW2 in parentRef, then update it to GW3. with the new change, GW1, GW2 and GW3 are considered as impacted.
  • tested No.2 by hardcoding routeGeneration from generateRouteData to be 1, thus nothing is updated since 1 is less than current generation
• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[k8s-ci-robot]

Hi @shuqz. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[zac-nixon]

You can utilize a set:

import "k8s.io/apimachinery/pkg/util/sets"
sets.Set[types.NamespacedName]

[zac-nixon]

please remove :)

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: shuqz, zac-nixon

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• OWNERS [zac-nixon]

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[zac-nixon]

/ok-to-test
/approved

[zac-nixon]

/lgtm